Testing of hair samples for the presence of indicators of drug use has gained importance not only for evidence gathering for criminal justice system proceedings but in pre-employment and post-employment screening of individuals. Unlike urine or blood sample testing which can provide only short term information concerning drug use by the tested individual and can therefore produce a negative result through abstention preceding the taking of the sample, hair testing can provide a long-term history of drug use for periods of, for example, ninety days or more preceding the taking of the sample. For this reason hair testing for drug use has become a reliable and important pre-employment or periodic test which cannot be defeated by short term abstention.
Heretofore testing of hair samples for drug use of marijuana, phencyclidine (PCP), opiates, cocaine, amphetamine and methamphetamine has been through techniques such as radioimmunoassay (RIA), gas chromatography-mass spectrometry (GC/MS)and tandem gas chromatography-mass spectrometry (GC/MS/MS). These techniques not only qualitatively produce data indicative of the presence or absence of indicators of drug use from a hair sample but also quantify those results. These assays are expensive and time consuming. What is needed is a relatively fast and economical method for conducting a series of screening tests which identify clearly negative samples, i.e. samples with no, or less than threshold amounts, of indicators of use of such drugs, from samples which are positive or not clearly negative. By performing a screening test series on the samples, the necessity of performing complicated, expensive and time consuming assays including GC/MS or GC/MS/MS on determined negative samples would be obviated. Such elaborate assays would be reserved for those samples which, by the screening series, were positive or otherwise not clearly identifiable as negative. Reserving the use of GC/MS and like assays, to samples which are not identified by the screening series as clearly negative, would result in savings in time, reduced workload schedule for expensive assay equipment as well for laboratory personnel.
An appropriate series of screening tests, is a series forensically sustainable in their own right and accordingly must use generally accepted scientific techniques and principles.
Enzyme linked immunosorbant assay (ELISA) has been used for analyzing urine and blood samples to determine the presence of cannabinoids. ELISA is, compared to the other assays such GC/MS and GC/MS/MS, relatively inexpensive, fast and accurate to determine the presence of target analytes indicative of use of certain drugs of abuse. However, attempts to use ELISA as a screening test for cannabinoids on hair sample extracts has heretofore been unsuccessful. ELISA relies upon immunospecific reactions of the analytes to test for the presence of substances. ELISA testing is well known, is described in U.S. Pat. No. 4,952,517 issued Aug. 28, 1990 and accordingly will not be described herein. It is believed that procedures heretofore used for obtaining the hair extract containing the many cannabinoid analytes have been frustrated by adherence of these analytes or unknown amounts thereof on analytical surfaces resulting in the inability to correlate the results of the assay with the actual presence or absence of the analytes being tested for. Accordingly ELISA has not been successful as a test for cannabinoid analytes extracted from hair samples.
It would be useful if ELISA for cannabinoids could be incorporated into a sample screening test series.
It has been known to use ELISA to sample for amphetamine and methamphetamine analytes in urine and blood samples. However, to our knowledge such sampling has not been used on hair samples as part of an overall series of sample screening tests.
It is also known to use radio immunoassay (RIA) to test hair samples for the presence of analytes indicative of use of opiates, cocaine and PCP. RIA, as is known, tags target analytes with a radioactive marker which can be scanned for and read.